Method of making twisted boring-tools



(No Model.) I

- w 0. ROBIN.

METHOD OF MAKING TWISTED BORING TOOLS.

Patented June 2, 1885.

INVENTOR ATTORNEYS.

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NITED STATES Pare'r twice.

CHARLES ROBIN, OF CHESTER, CONNECTICUT.

METHOD OF MAKING TWISTED BORING-TOOLS.

SPECIFICATION forming part of Letters Patent No. 319,027, dated June 2, 1885.

Application filed April 2, 1884.

To all whom it may concern:

Be it known that I, CHARLES ROBIN, of Chester, in the county of Middlesex and State of Connecticut, have invented a new and Irnproved Method of Making Twisted Boring- Tools, of which the following is a full, clear, and exact description.

My invention relates to improvements in the process of forming that class of twisted boring-tools employed in boring wood, metals, and other substances; and it consists in swaging a blank with a plane and concave side, and then twisting the same to form a bit with a deep spiral groove on one side and a shallow spiral groove on the opposite side, as will be hereinafter described and claimed.

Reference is to be had tothe accompanying drawings, forming part of this specification, in which similar letters of reference indicate corresponding parts in all the figures.

Figure l is a side elevation of a bit made in accordance with my invention. Fig. 2shows the unfinished bit before sharpening. Fig. 3 is a front elevation, and Fig. 4 a longitudinal section, of the bit-blank. Fig. 5 is an enlarged side elevation of a portion of the body ofa bit. Fig. 6 is a transverse section taken on line 00 x in Fig. 3, and Fig. 7 is a transverse section taken on line y y in Fig. 5.

The bit made by my improved method has a twisted body, A, in which are formed two spiral grooves, B C. The groove B is very shallow, and is designed to relieve the bit of friction and to carry out of the hole being bored any small particles or dust that may escape the groove C.

The groove 0 is of such (No model.)

depth as to reach into the body of the bit beyond its axial line, forming a deep channel for the escape of chips, and at the same time securing acute cutting-edges D, which bore rapidly and easily, and leave a clean smooth hole in the wood or other material being bored.

To make my improved bit I form on the shank E a flat rectangular end, which Iswage so as to make one side thereof concave from the shank to the extremity, as shown in Figs. 3, 4, and 6. Ithen twist the blank into the form shown in Fig. 2. The twisting of the blank renders the plane side thereof slightly concave and forms the groove B. It also increases the concavity of the swaged side, and forms the deep groove 0, which extends inward beyond the axial line of the bit. The bit thus formed requires very little grinding to produce the sharp gouge-like edges D D, which cut freely and form chips which are readily carried out of the hole being bored by the deep groove 0.

Having thus fully described myinvention, I claim as new and desire to secure by Letters Patent- Themethod of making a boring-bit which consists in swaging a blank with a plane and a concave side, and twisting the same to form a bit with a deep spiral groove on one side and a shallow spiral groove on the opposite side, as specified.

CHARLES ROBIN.

\Vitnesses:

Gosmv A.STA1\'GER, JAMES R. FERGUSON. 

